Machines such as skid steer loaders, multi-terrain loaders, track-type tractors, tracked loaders, etc., generally have an engine powering some type of hydraulic system for propelling the machine or providing hydraulic power to linkages. These engines are typically cooled by a cooling system having a radiator and cooling fan. Some machine designs use a belt driven cooling fan with a fan speed fixed proportionally to the engine speed.
In some applications, it may be desired to provide retarding to assist in controlling the speed of the machine and engine when operating in downhill conditions. Machines having belt-driven cooling fans automatically provide an increase in torque resistance during such conditions. However, in an effort to increase machine efficiency, machines have been developed that replace the belt driven cooling fan with an electronically controlled hydraulically driven demand fan. These fans are operated only when required by engine cooling demands. This has the effect of increasing machine efficiency and fuel economy, as the engine does not have to drive the cooling fan load under all conditions. While the overall machine efficiency has increased, these machines having hydraulically driven demand fans have lost the retarding effect that the belt-driven fan had on the engine and machine during overspeed conditions.
The present disclosure is directed to overcoming one or more of the problems as set forth above.